/Engine/Source/Runtime/Engine/Classes/Engine/GameEngine.h
Determines the resolution of the game window, ensuring that the requested size is never bigger than the available desktop size
static void DetermineGameWindowResolution ( int32 & ResolutionX, int32 & ResolutionY, [EWindowMode::Type](API\Runtime\ApplicationCore\GenericPlatform\EWindowMode__Type) & WindowMode, bool bUseWorkAreaForWindowed )